Multicomponent Silicate Glasses Research Articles

UVC Up-Conversion and Vis-NIR Luminescence Examined in SrO-CaO-MgO-SiO2 Glasses Doped with Pr3.

The application of ultraviolet-C light in the field of surface treatment or photodynamic therapy is highly prospective. In this regard, the stable fluorescent silicate SrO-CaO-MgO-SiO2-Pr2O3 glasses able to effectively convert visible excitation on the ultraviolet praseodymium emission were fabricated and examined. An unusual wide-range visible-to-UVC up-conversion within 240-410 nm has been achieved in Pr3+-doped glasses, revealing their potential advantage in different sophisticated disinfection technologies. The integrated emission intensity was studied as a function of light excitation power to assess a mechanism attributed to UVC luminescence. Especially, it was revealed that the multicomponent silicate glass qualities and praseodymium 3PJ excited state peculiarities are favorable to obtaining useful broadband ultraviolet up-converted luminescence. The glass dispersion qualities were determined between 450-2300 nm. The impact of praseodymium concentration on Vis-NIR spectroscopic glass qualities was evaluated employing absorption spectra, emission spectra, and decay curves of luminescence associated with two involved praseodymium excited states. Especially, efficient interionic interactions can be inferred by investigating the decrease in 1D2 state experimental lifetime in the heavily doped samples. Examination of absorption spectra as a function of temperature implied that excitation at 445 nm should be quite effective up to T = 625 K. Contrary to this, temperature elevation gives rise to a moderate lowering of the visible praseodymium luminescence.

Thermogravimetric and temperature-dependent electrical investigations of Pr3+ doped multi-component silicate glasses for microelectronic technology

Multi-component silicate glasses doped with 0, 0.5, 1, and 1.5 mol% of praseodymium (Pr3+) were synthesized by the sol–gel method. Thermal analysis of the glasses, evinced a high working temperature of 351 °C and Hruby coefficient, K H = 1.415 in the highly doped system, corroborating the effective role of Pr3+ ions in endowing superior thermal stability to the glass. Broadband dielectric spectroscopy was applied to study the temperature-dependent electrical behavior of the glasses for their suitability as electrodes and solid electrolyte materials in batteries. A high dielectric constant of 4797 was evidenced at 1 kHz when recorded at 473 K. The AC conductivity of the glass doped with 1 mol% was observed to be the highest with 94.8 × 10−5 S cm−1 at 10 MHz and 473 K. Jonscher’s power law exponent decreased with temperature, attributing the conducting mechanism to the Correlated Barrier Hopping (CBH) model. The Nyquist impedance spectra demonstrated a depressed semicircle with a spur at the low-frequency end, validating the non-Debye relaxation in the glasses. The equivalent circuitry of the plot predicted parallel combinations of resistor and constant phase elements which reflects a Warburg diffusion and capacitive approach. Bode’s phasor diagram confirmed the capacitive nature by a phase angle of −90° in all the glasses. While a uniform increase in dielectric constant and conductivity was observed up to 1 mol% of Pr3+, a sharp decline in the electrical phenomenon was observed with 1.5 mol% of Pr3+, due to the possible blockade of the hopping of charge carriers by the largely quantified dopant ions. Extracting a high dielectric constant, and ionic conductivity at high frequencies, with an optimal dopant concentration of 1 mol% Pr3+, the composite glasses could be considered for their potential use in integrated microcomponent storage devices as cathode and solid electrolyte materials.

Effect of Y2O3 Concentration on the Surface and Bulk Crystallization of Multicomponent Silicate Glasses

Multicomponent silicate glasses are crystallized by Y2O3 addition. Depending on the Y2O3 concentration, different crystalline phases evolve. In the absence of Y2O3, a multicomponent glass crystallizes as ZnSnO3, while with the addition of just 3% of this oxide, ZnSnO3 no longer crystallizes and ZrSiO4 appears instead. Different yttrium silicate crystals are formed in all glasses containing Y2O3, but, while α-Y2Si2O7 and β-Y2Si2O7 are favored at low Y2O3 concentrations, the γ-Y2Si2O7 and y-Y2Si2O7 phases are favored at the maximum Y2O3 content. At a 12% Y2O3 concentration, barium and calcium silicate crystalline phases also evolve. Interestingly, the crystalline phases appearing on the surface of the material present different microstructures compared to crystals developed in the bulk. While the crystallized surface presents a tabular-shape type, crystallization in the bulk is of a prismatic type at low Y2O3 concentrations and of a globular (spherical) type at higher concentrations. The main crystal size ranges between 0.85 and 0.75 micrometers, but most of the crystals coalesce to form larger superstructures depending on the Y2O3 concentrations.

Boroaluminosilicate glass-ceramics containing mullite-type Cr3+:Al4B2O9 nanocrystals with broadband near-infrared luminescence

Multi-component silicate glass is an ideal matrix for fabricating glass-ceramics because of its excellent physical-chemical stability and high optical transmittance. In this paper, a series of Cr3+ doped multi-component silicate glasses were designed for the preparation of glass-ceramics that crystalizes mullite-type Cr3+:Al4B2O9 nanocrystals. When excited at 450 nm, the obtained GCs exhibit a broadband NIR luminescence band covering a spectral region from 650 to 1200 nm. Two different crystallographic sites of Cr3+ in Al4B2O9 nanocrystal are considered to account for the observed broadband luminescence. Due to the controllable size and uniformly dispersion of precipitated nanoparticles, this boroaluminosilicate glass-ceramic could find potential applications as monolithic near-infrared light sources in solid-state light emitting devices.

Cyclic ablation resistance at 2300 °C of (Hf0.4Zr0.4Ta0.2)B2-SiC-Si coating for C/SiC composites prepared by SiC-assisted reactive infiltration of silicon

Developing coatings is of prime importance for improving the ablation resistance of Cf/SiC composites at ultra-high temperatures due to the inherent preparation defects in the SiC matrix and the low melting point of the produced SiO2. In this paper, a (Hf0.4Zr0.4Ta0.2)B2-SiC-Si (HZTS) coating with a quaternary solid solution of ultra-high temperature boride was designed and coated on the surface of Cf/SiC substrate by SiC-assisted reactive infiltration of silicon. The obtained HZTS coating has a high interfacial bonding strength of 18.25 MPa with the substrate due to its dense structure and uniform constituent distribution, as well as their physical and chemical adhesion. The coating also presents an excellent cycle ablation resistance with a respective mass and linear ablation rates of 2.1 × 10−2 mg/s and 0.4 μm/s after 15 cycles of 60 s ablation at 2300 °C, which are attributed to the formation of highly thermo-stable Hf-Zr-Ta-O solid solution and multicomponent silicate glass.

Insights into the mechanism and kinetics of dissolution of aluminoborosilicate glasses in acidic media: Impact of high ionic field strength cations

Achieving thinner and higher performance display/substrate glasses and transparent glass-ceramics with tunable properties requires a precise control of acid-etching process, thus necessitating a comprehensive understanding of glass composition–structure–dissolution behavior relationships in acidic medium. Unfortunately, the literature on this subject has been focused only on a narrow set of glass chemistries. Therefore, consensus on the mechanisms that govern the acidic dissolution of multicomponent silicate glasses over a broad compositional space is still lacking. The present work employs a suite of state-of-the-art spectroscopic techniques, including 1D and 2D NMR, TEM-EELS, ICP-OES, and XPS, to provide an insight into the mechanism and kinetics of corrosion of alkali/alkaline-earth aluminoborosilicate glasses (comprising high field strength cations – HFSCs, i.e., La3+, Ti4+, Zr4+ and Nb5+) in acidic media (HCl; pH = 2). Incorporating the HFSCs into the glasses induces significant structural changes in their network, thus, impacting the forward rate dissolution kinetics. Based on the results, we hypothesize that the glasses dissolve at pH = 2 through an ‘interfacial dissolution – re-precipitation mechanism (IDPM)’ and ‘in-situ recondensation’ coupled pattern, wherein the IDPM results in a Si-rich alteration layer, followed by local recondensation occurring due to limited kinetics near the interfacial solution between the uncorroded glass surface and the outer alteration layer.

Near-infrared photoluminescence properties of Er/Yb- and Ho/Yb-doped multicomponent silicate glass – The role of GeO2, Al2O3 and ZnO

We prepared multicomponent silicate glass, which contained components with different glass-forming abilities, such as GeO2, Al2O3 and ZnO, or different concentrations of glass-modifier oxide Na2O. The influence of the glass composition on the network structure and its effect on the photoluminescence properties of rare-earth ions were investigated. It was found that a change in the Na2O content significantly affects the network polymerisation, but its influence on the photoluminescence of RE ions is limited. The photoluminescence properties of RE ions were significantly influenced by the presence of different components, such as GeO2, Al2O3 and ZnO, which was attributed to changes in the local environment of RE ions. ZnO induced highest asymmetry of host matrix around the RE ions, which led to a strong and broad photoluminescence with short fluorescence lifetime, whereas the inclusion of Al2O3 and GeO2 led to highly symmetric matrix with narrow emission bands and longer decay.

Evolution of the structure and chemical composition of the interface between multi-component silicate glasses and yttria-stabilized zirconia after 40,000 h exposure in air at 800 °C

The chemical and structural stability of two commercial multicomponent silicate glasses (SCN and G6) in contact with yttria-stabilized zirconia (YSZ) was investigated after exposure times of up to 40,000 h in air at 800 °C. With exposure time, interfacial layers develop at the SCN-YSZ and G6-YSZ interfaces, which were characterized in detail using both quantitative chemical analysis and atomic-resolution imaging. At the SCN-YSZ interface, a Ca-Ba-Si-O reaction phase was found to grow by diffusion control. In G6-YSZ, Raman spectroscopy and electron microscopy revealed a disorganized interfacial reaction later between G6 and YSZ, and the occurrence of cubic to tetragonal to monoclinic phase transformations in YSZ. This microstructural evolution is discussed in terms of devitrification resistance of glass and diffusion processes at interfaces.

Nd3+ doped multi-component phosphate glass multi-material fiber for a 1.05 μm laser

Nd3+ doped multi-component phosphate glass was prepared by the conventional melt-quenching method. The absorption spectrum, emission spectrum, and fluorescence lifetime of the prepared glass were measured. Based on the absorption spectrum, Judd-Ofelt (J-O) intensity parameters, spectroscopic quality factor, absorption and emission cross-sections, and figure of merit were calculated and analyzed. What is more, multi-material fibers with Nd3+ doped multi-component phosphate glass core and silicate glass cladding were successfully drawn by using the molten core method. The Nd3+ doping concentration reaches as high as 3.82 × 1020 ions/cm3 (3.86 wt.%). More importantly, 1.05 μm amplified spontaneous emission (ASE) was realized in a 4-cm-long as-drawn multi-material fiber when pumped by an 808 nm laser diode (LD). These results suggest that the Nd3+ doped multi-component phosphate glass multi-material fibers are promising gain material for 1.05 μm fiber laser applications.

Structure and disorder in Pb‐Na metasilicate (PbO:Na2O:2SiO2) glasses: A view from high‐resolution 17O solid‐state NMR

AbstractKnowledge of the structure of lead (Pb)‐bearing silicate glasses, such as degree of polymerization and arrangement among cations, provides improved prospects for understanding their macroscopic properties. Despite the importance, the detailed disorder in Pb‐bearing silicate glasses with varying composition (i.e., Pb/alkali content) has not been systematically explored. Here, we reveal the first unambiguous structural information of PbO‐Na2O‐SiO2 glasses with varying PbO content [i.e., XPbO = PbO/(Na2O + PbO)], which are the fundamental model system for multicomponent Pb‐bearing glasses, using high‐resolution 17O solid‐state NMR. 17O NMR spectra clearly show the resolved multiple oxygen sites, such as Na‐O‐Si, Si‐O‐Si, and [Na,Pb]‐O‐Si. As XPbO increases, the fraction of [Na,Pb]‐O‐Si peak increases markedly at the expanse of substantial reduction in the fraction of Na‐O‐Si/total NBO. This trend indicates the relative predominance of the dissimilar pairs around non‐bridging oxygen (NBO) and, therefore, can be explained well with the pronounced chemical ordering among Na+ and Pb2+. These results confirm that Pb is primarily a network‐modifier in the glasses studied here. Atomic environments around both NBO and BO are affected by the change in Na/Pb ratio, while topological disorder due to cation mixing around NBO is much more prominent in Pb endmember. The structural details of short‐range configurations around oxygen in alkali Pb‐silicate glasses provide atomistic insights for understanding the properties of Pb‐bearing multicomponent silicate glasses.

Water adsorption on silica and calcium‐boroaluminosilicate glass surfaces—Thickness and hydrogen bonding of water layer

AbstractAdsorption isotherm of water on silica (modeled with fused quartz) and calcium‐boroaluminosilicate (Ca‐BAS) glass surfaces as a function of relative humidity (RH) was studied using Fourier transform infrared (FTIR) spectroscopy. The effective thickness of the adsorbed water layer and the distribution of hydrogen bonding interactions of water molecules in the adsorbed layer were determined by comparing the transmission FTIR spectra collected at the Brewster incidence angle with the theoretically calculated spectra. In the sub‐monolayer regime (<30% RH), differences between the water spectra on fused quartz and Ca‐BAS glass could be related to the areal density of hydroxyl groups as well as the elemental composition of the surface determined with x‐ray photoelectron spectroscopy. In the transition regime (30%–60% RH), multilayers start growing and the difference between the fused quartz and Ca‐BAS surfaces diminishes as the humidity increases. In the multilayer regime (>60% RH), the total amount as well as the hydrogen bonding interactions of adsorbed water layers become insensitive to the surface chemistry and are governed mostly by the phase transition (vapor condensation) behavior. Overall, this study reveals how the water layer thickness and structure on the multicomponent silicate glass surface in ambient conditions are different from those on the pure silica surface.

A Raman spectroscopic tool to estimate chemical composition of natural volcanic glasses

A correlation between Raman spectra of silicate glasses and their chemical composition is investigated using a collection of 31 natural multicomponent silicate glasses. The sample suite comprises the largest database of Raman spectra collected on natural volcanic materials and spans subalkaline to Na-rich and K-rich alkaline compositions. Raman spectra were acquired using a Nd solid state green laser having an excitation wavelength of 532 nm. The model was verified against an independent database of 8 additional samples (i.e. not used for calibration). Ratios of Raman peaks (R, Rn) retrieved from spectra are shown to have a strong covariance with concentrations of six oxides (SiO2, TiO2, Al2O3, FeOT, MgO and CaO) across the compositional range of the sample suite. The Raman ratios are also strongly correlated to pseudo-structural parameters (e.g., NBO/T, SM) calculated from oxide concentrations of SiO2, TiO2, Al2O3, FeOT, MgO, CaO, Na2O and K2O. The Raman ratios are relatively insensitive to variations in Na2O and K2O contents and, as a consequence, their concentrations can only be estimated if additional independent constraints on chemical content are available. This work constitutes the first generalized model for retrieving chemical compositions of natural glasses from corresponding Raman spectra. The model provides a rapid, robust and inexpensive way to retrieve compositions of volcanic glasses in both laboratory and field environments and thus represents a powerful new tool for earth and planetary, archaeological and glass sciences. A similar strategy can be applied to silicate melts and glasses used in industrial activities.

Hydration and reaction mechanisms on sodium silicate glass surfaces from molecular dynamics simulations with reactive force fields

AbstractRecent development of reactive force fields have enabled molecular dynamics simulations of interactions between silicate glasses and water at the atomistic scale. While multicomponent silicate glasses encompass a wide variety of compositions and properties, one common structural feature in these glasses is the combination of the network structure that is made up of silica tetrahedra linked through corner sharing interspersed with network modifiers like alkali and alkaline‐earth ions that break up the Si–O–Si linkages by forming nonbridging oxygen. In reactions with water, ion exchange between alkali ions in the glass and proton or hydronium in the solution, as well as hydrolysis reaction of the Si–O–Si linkages and subsequent silanol formation, is observed and well documented. We have used a set of recently developed reactive force field to investigate the reactions between water and the surfaces of silica and sodium silicate glasses of different compositions for reactions up to 8 nanoseconds. Our results indicate sodium leaching into water and diffusion of water molecules up to 25 Å into the glass surface. We examined the structural and compositional changes inside the glass and around the diffused ions and use these to explain the rates of silanol formation at the surface. We also observed proton transport in the glass which has an indirect influence on the silanol formation rates. While the surface of the glass was rough to start with, it undergoes further modification into a hydrated gel‐like structure in the glass for up to 5 Å in the higher alkali containing glasses. It was found that the leached sodium ions remain close to the interface and that fragments of silicate network from the surface is capable of dislodging from the bulk glass and enter the aqueous solution. These simulations thus provide insights into the formation and structure of an alteration layers commonly observed in multicomponent silicate glasses corroded in aqueous solutions.

Spatial charge relaxation in glasses poled in the air and argon atmospheres

Thermal poling of a multicomponent silicate glass was performed in air and in argon atmospheres at various voltages, and the temperature dependences of the depolarization currents (TSDC) in the poled glasses were studied. In addition, the concentration profiles of univalent and bivalent cations in subanodic regions of the poled glasses were measured with EDS and SIMS techniques. The difference in the displacements of bivalent ions at poling of the glasses in closed and open anode configurations allowed us to identify “frozen” spatial charge relaxation peaks observed in the TSDC measurements and to relate these peaks to hydrogen and bivalent metal ions relaxation.

Response to comments on “How to reveal the correct elemental concentration profiles in poled multicomponent silicate glasses from the data of secondary ion mass spectrometry (SIMS)”

Response to comments on “How to reveal the correct elemental concentration profiles in poled multicomponent silicate glasses from the data of secondary ion mass spectrometry (SIMS)”

A calibrated database of Raman spectra for natural silicate glasses: implications for modelling melt physical properties

AbstractThe physical properties of silicate melts are of critical importance for understanding magmatic and volcanic processes on Earth and other planets. Most physical properties of melts are, ultimately, a consequence of the structural organization of the melt. Robust and fully generalizable strategies for the prediction of properties of naturally occurring melts as functions of composition, temperature, and pressure remain a challenging goal. Given the structural origin of macroscopic properties, Raman spectroscopy of glasses, which provides information on melt and glass structure, may provide a useful technique to understanding and quantify variations in macroscopic melt properties. Here, with the aim of providing a generalizable model for predicting the viscosity of silicate melts, we present the results of a Raman spectroscopy campaign performed on 30 anhydrous multicomponent silicate glasses resulting from quenching of remelted and homogenized volcanic rocks and synthetic equivalents. The sample suite comprises one of the largest databases of multicomponent melts for which (a) chemical compositions and (b) physical properties (i.e., viscosity, fragility, heat capacity, and glass transition temperature) are known. Raman spectra have been collected using green light sources at wavelengths of 532 nm. Spectra were collected on the same sample suite in four independent laboratories involving instruments from different manufacturers and, thus, using different spectrometers, detectors, and analytical conditions. Our results are also compared and integrated with published data on some of the same samples derived from two others setups using green light sources with 514.5 and 532 nm wavelegths. For the same sample, the Raman spectra acquired using different setups show different intensities and intensity ratios. However, a strategy based on the ratio between the low‐ and high‐wavenumber peaks (R) was developed to standardize the data to normalized Raman ratios (Rn) and thus to remove interlaboratory differences. Using these advances, we predict melt viscosity solely with the use of Raman spectral measurements of multicomponent silicate glasses, thus demonstrating the potential of the method in describing physical properties of silicate melts.

Comments on “How to reveal the correct elemental concentration profiles in poled multicomponent silicate glasses from the data of secondary ion mass spectrometry (SIMS)”

In the recent article entitled “How to reveal the correct elemental concentration profiles in poled multicomponent silicate glasses from the data of secondary ion mass spectrometry (SIMS),” a SIMS data treatment is proposed, and is predicated on the assumption of the “true” depth profile for poled glasses having a fixed concentration of network-formers like silicon, under the auspices of such species being “immovable” during poling. Deliberated herein are the assumptions underlying this treatment, and particularly highlighting experimental evidence that should lead one to expect that the volumetric concentration of network-formers like silicon should, in fact, be altered during poling (through effects such as network repolymerization). These points cast serious concerns on the fundamental premise underlying the data treatment.

Surface Reactivity and Leaching of a Sodium Silicate Glass under an Aqueous Environment: A ReaxFF Molecular Dynamics Study

The presence of leachable ions in multicomponent silicate glasses complicates the understanding of their surface structure and chemistry under a humid or aqueous environment, in particular when com...

Broadband blue emission from ZnO amorphous nanodomains in zinc phosphate oxynitride glass.

ZnO amorphous nanostructures in a glass matrix show unique optical properties. However, although a ZnO amorphous nanostructure can be formed in some settled multicomponent silicate glasses, the intensity of its emission is extremely weak. Here, to the best of our knowledge, we report a novel and simple zinc phosphate oxynitride glass that can display strong broadband blue emission with a short decay time due to the ZnO amorphous nanostructure in the glass matrix. The result implies that glass topological constraints are the key to forming ZnO amorphous nanostructures. The findings contribute to a deeper understanding of the formation of ZnO amorphous nanostructures in zinc-containing glass.

Structural and Chemical Approach toward Understanding the Aqueous Corrosion of Sodium Aluminoborate Glasses

Despite an ongoing strenuous effort to understand the compositional and structural drivers controlling the chemical durability of oxide glasses, there is still no complete consensus on the basic mechanism of glass dissolution that applies to a wide composition space. One major reason for this problem is the structural complexity contained within the multicomponent silicate glasses chosen for glass corrosion studies. The nonsilicate network polyhedra present in these glasses interact with one another, often in unpredictable ways, by forming a variety of structural associations, for example, Al[IV]-B[III] and B[III]-B[IV], resulting in significant influence on both the structure of the glass network and related macroscopic properties. Likewise, the formation of a variety of next-neighbor linkages, as well as increasingly complex interactions involving Si and differently coordinated next-nearest neighbor cations, is very difficult to decipher experimentally. Consideration of these factors motivates instead a different strategy: that is, the study of a sequence of SiO2-free ternary or quaternary glass compositions, whose structures can be unambiguously determined and robustly linked to their corrosion properties. With this aim, the present study is focused on understanding the structural drivers governing the kinetics and mechanism of corrosion of ternary Na2O-Al2O3-B2O3 glasses (in water) over a broad composition space comprising compositions with distinct structural features. It has been shown that the addition of Al2O3 to binary sodium borate glasses decreases their corrosion rate in water and converts their dissolution behavior from congruent to incongruent leading to the formation of six-coordinated alumina, and higher concentration of four-coordinated boron (in comparison to pre-dissolution glasses) in post-dissolution glass samples. The drivers controlling the corrosion kinetics and mechanism in these glasses based on their underlying structure have been elucidated. Some open questions have been proposed which require an extensive analysis of surface chemistry of pre- and post-dissolution samples and will be investigated in our future work.